The curing of monomeric materials to produce thermoset resins is well known in the art. In general, the curable monomers have at least one and customarily more than one active group which serves as the reactive site for a curing or crosslinking reaction to produce the cured thermoset resins which are typically highly crosslinked. The curing or crosslinking of many thermoset resins, for example, the curing of epoxy resins, requires the use of a curing agent, catalytic or stoichiometric, to cause the crosslinking reaction to proceed at an acceptable rate. Certain other monomers cure in the absence of added curing agent, but only upon application of high intensity energy, e.g., UV light. Even in the presence of most curing agents the rate of crosslinking is unduly slow and the addition of an accelerator is generally required to obtain sufficiently rapid curing.
There are some monomers in which the active sites are such that no added curing agent is required and such monomers cure upon application of heat at an acceptable rate. These monomers are termed "self-curing". One class of the self-curing monomers includes within the molecular structure one or more moieties of an arylcyclobutene, preferably a benzocyclobutene. These monomers are cured by reaction with a conventional curing agent but are also self-curing. Without wishing to be bound by any particular theory, it appears probable that upon application of heat the cyclobutene ring undergoes ring opening to produce active intermediates which crosslink by undergoing rapid reaction with adjacent molecules. The resulting cured thermoset resins have properties of rigidity and strength.
A series of U.S. patents to Kirchhoff, of which U.S. Pat. No. 4,540,763 is illustrative, describes the production and curing of a large number of benzocyclobutene derivatives, including ethers of bis(hydroxyphenyl)alkanes, wherein the ether linking group which links the phenyl of the bis(hydroxyphenyl)alkane to the benzocyclobutene moiety is attached directly to the six-membered ring of the benzocyclobutene. A U.S. patent to Tan et al, U.S. Pat. No. 4,675,370, discloses benzocyclobutene derivatives in which the six-membered ring of the benzocyclobutene is attached to a substituent having an acetylenic group by an aromatic link. A related series of Wong, of which U.S. Pat. No. 4,687,815 is illustrative, discloses alkenyl substituted benzocyclobutenes. A Research Disclosure, source unknown, discloses benzocyclobutenes in which the six-membered ring of the benzocyclobutene is attached to a polyvalent organic or inorganic group which is preferably hydrocarbon or contains silicon, nitrogen or oxygen heterocyclic moieties. A somewhat different type of benzocyclobutene ether derivative is disclosed and claimed by copending U.S. patent application Ser. No. 349,546, filed, May 9, 1989 U.S. Pat. No. 4,943,665 directed to benzocyclobutenealkyl ethers of bis(hydroxyphenyl)alkanes. These ethers have an alkylene linking group attached to the six-membered ring of the benzocyclobutene ring system and through an ether oxygen is attached to the phenyl group of the bis(hydroxyphenyl)alkane. Other ethers having a hydroxyaryl-substituted 1,6-diaza [4.4] spirodilactam group present are disclosed and claimed in copending U.S. patent application Ser. No. 245,433, filed Sept. 16, 1988 now U.S. Pat. No. 4,897,388. Alkenyl and alkenyl esters, e.g., allyl or propargyl ethers of 1,6-di(4-hydroxyphenyl)-1,6-diazaspiro4.4]nonane-2,7-dione, are illustrative and are disclosed as being self-curing.
It would be of advantage, however, to provide additional benzocyclobutene-type ether derivatives wherein other polycyclic structures are present.